Superconductivity Discovered

On April 8, 1911, during a study of the resistance of solid mercury at very
cold temperatures, superconductivity was discovered by Heike Kamerlingh Onnes.
Electrical resistance, a sort of electric friction, results in heat loss.
Scientists had begun believing in the late 1800s that low temperatures could
result in a reduction or lack of electrical resistance, but it was not until
Onnes produced liquid helium in 1908 that more in-depth research could be
performed. Using his newly discovered liquid helium, Onnes began looking at the
resistance of platinum and gold at cold temperatures, but it was the use of
mercury that proved successful. As the temperature of the liquid helium
decreased, so did the resistance of the mercury, until the temperature of 4.19
Kelvin, when the resistance disappeared. A total lack of electrical resistance
became known as superconductivity.

Most substances cannot superconduct,
but the ones that can are known as superconductors. As temperatures drop, the
superconductor experiences less and less electrical resistance, until reaching a
certain temperature when resistance disappears and the superconductor undergoes
a phase change. Types of superconductors are established based on their response
to magnetic fields, critical temperatures, and materials. Magnetism is an
integral part of superconductivity and it works because of the Meissner effect,
where a superconductor expels its magnetic field.

Superconductivity is
used in a variety of applications. MRI and NMR machines use superconducting
magnets to create medical images. High-energy particle acceleration requires the
use of superconductor magnets. Superconducting magnets are also used in maglev
trains, such as the Shanghai Maglev Train in China and SCMaglev in Japan.
Electric generators use superconducting wires to be more efficient and reduce
heat loss.